What are gangs trying to achieve?

http://www.brownsvilleherald.com/articles/mexico-132121-rivals-city.html

• Las pandillas espantan los rivales.La MS 13 pandilla se encontraba en lo porbreza y no veia ninguna esperanza en su futuro por lo que emperzon una pandilla y ahora son la pandilla mas peligrosa del mundo.
  Los Mastros mexicanos estan luchando contra las pandillas, las pandillas quieren dinero y la otra mitad de la paga de los profesores.

Mexican gangs are trying to scare off rivals
http://ms13gang.com/

• The MS 13 gang was in poverty and saw no hope in their future so they started a gang and are now the most dangerous gang in the world.

http://www.nytimes.com/2011/09/26/world/americas/mexican-teachers-push-back-against-gangs-extortion-attempts.html?pagewanted=all

• The mexican teachers are fighting back against gangs, the gangs want money and half of the teacher's pay.

Mexican teachers heads chopped off because wouldn't give up half of their pay